The present invention relates to a one-way clutch for use in a transmission of an automobile.
As a one-way clutch for use in a transmission of an automobile or the like, one is conventionally known such as in Japanese Examined Utility Model Publication No. Hei. 7-55391. FIG. 8 shows a related one-way clutch and it includes an outer race 50, an inner race 51, a plurality of engaging members (sprags) 52 disposed between the inner and outer races, an inner retainer 53, an outer retainer 54, springs 55, a pair of end bearings 56, and the like.
The aforementioned sprags 52 are retained by the inner retainer 53 and the outer retainer 54 in a space formed by the end bearings 56 fitted to opposite sides between the inner race 51 and the outer race 50, and are disposed in such a manner as to be urged in one direction by the springs 55 disposed between the inner and outer retainers 53 and 54. Each end bearing 56 is formed into a U-shaped cross section and is constituted by a first hollow cylindrical portion 57 fitted to an outer peripheral surface 51a of the inner race 51, a second hollow cylindrical portion 58 fitted to an inner peripheral surface 50a of the outer race 50, and an annular portion 59 which radially connects the first hollow cylindrical portion 57 to the second hollow cylindrical portion 58. The annular portion 59 of each end bearing 56 having the U-shaped cross section is located on each outer side of the one-way clutch. Each annular portion 59 has substantially the same thickness from its inner periphery to its outer periphery and is formed in such a manner as to extend radially so as to be substantially perpendicular to the axis of the inner race 51. In each of the end bearings 56, an inner peripheral surface 57a of the first hollow cylindrical portion 57 opposing the outer peripheral surface 51a of the inner race 51, as well as an outer peripheral surface 58a of the second hollow cylindrical portion 58 opposing the inner peripheral surface 50a of the outer race 50, are formed as smooth surfaces.
In the above-described conventional one-way clutch, the end bearings 56 are disposed between the inner and outer races 51 and 50 and have a function as slide bearings. Namely, the inner peripheral surface 57a of the first hollow cylindrical portion 57 slides on the outer peripheral surface 51a of the inner race 51, and the outer peripheral surface 58a of the second hollow cylindrical portion 58 slides on the inner peripheral surface 50a of the outer race 50. The clearance between the inner race 51 and the first hollow cylindrical portion 57 of the end bearing 56 and the clearance between the outer race 50 and the second hollow cylindrical portion 58 of the end bearing 56 are made extremely small in view of securing the space for the sprags 52 of the one-way clutch. For this reason, there have been problems in that the friction, i.e., the drag torque, between the inner race 51 and the first hollow cylindrical portion 57 of the end bearing 56 and between the outer race 50 and the second hollow cylindrical portion 58 of the end bearing 56 cannot be made small, and that seizure is likely to occur. This friction constitutes a problem particularly between the inner race 51 and the first hollow cylindrical portion 57. The reason is that consideration is generally given to eliminate as much as possible the clearance between the outer race 50 and the second hollow cylindrical portion 58, which is located on the side where the peripheral speed is large, so as to prevent the occurrence of sliding between the two members 50 and 58, whereas a clearance is provided between the inner race 51 and the first hollow cylindrical portion 57, where the peripheral speed is small, so as to positively allow sliding to occur between the two members 51 and 57.
In addition, to overcome the above-described problems, an arrangement has been proposed in which, as shown in FIG. 9, axial grooves 60 are formed at a plurality of circumferential positions in the inner peripheral surface 57a of the first hollow cylindrical portion 57 of the end bearing 56 by lathe turning machining, so as to lower the contact area. However, since the processing of the axial grooves 60 is effected by machining, there are problems in that the cost becomes high, and that mass productivity is poor.
In view of the above-described problems, the object of the invention is to provide a one-way clutch which excels in mass productivity and in which friction is small.
The object of the invention is to provide a one-way clutch in which an axial groove for enlarging the amount of lubricating oil retained and enhancing the reduction of friction between the first hollow cylindrical portion and the inner race is formed in the inner peripheral surface of the first hollow cylindrical portion of the end bearing.
In order to solve the aforesaid object, the invention is characterized by having the following arrangement.
(1) A one-way clutch comprising:
an inner race;
an outer race;
a plurality of engaging members disposed between the inner and outer races;
retainers for retaining the engaging members;
springs for urging the engaging members in one direction; and
a pair of end bearings which are respectively disposed on opposite sides between the inner race and the outer race, each of the end bearings having a U-shaped cross section and including,
a first hollow cylindrical portion fitted to an outer peripheral surface of the inner race,
a second hollow cylindrical portion fitted to an inner peripheral surface of said outer race,
an annular portion connecting the first hollow cylindrical portion to second hollow cylindrical portion, and
a plurality of recessed portions formed at least in the inner peripheral surface of the first hollow cylindrical portion of each of the end bearings.
(2) The one-way clutch according to (1), wherein the recessed portions are a plurality of dimple-like dents.
(3) The one-way clutch according to (1), wherein the recessed portions are axial grooves formed by press forming.
(4) The one-way clutch according to (1), wherein the recessed portions are axial grooves formed by press forming and a circumferential groove formed by press forming so as to intersect the axial grooves.
(5) A one-way clutch comprising:
an inner race;
an outer race;
a plurality of engaging members disposed between the inner and outer races;
retainers for retaining the engaging members;
springs for urging the engaging members in one direction; and
a pair of end bearings which are respectively disposed on opposite sides between the inner race and the outer race, each of the end bearings having a U-shaped cross section and including,
a first hollow cylindrical portion fitted to an outer peripheral surface of the inner race,
a second hollow cylindrical portion fitted to an inner peripheral surface of said outer race,
an annular portion connecting the first hollow cylindrical portion to second hollow cylindrical portion, and
a plurality of projections formed at least on the inner peripheral surface of the first hollow cylindrical portion of each of said end bearings.
(6) A one-way clutch including:
an inner race;
an outer race;
a plurality of engaging members disposed between the inner and outer races;
retainers for retaining the engaging members;
springs for urging the engaging members in one direction; and
a pair of end bearings which are respectively disposed on opposite sides between the inner race and the outer race, each of the end bearings having a U-shaped cross section and including,
a first hollow cylindrical portion fitted to an outer peripheral surface of the inner race,
a second hollow cylindrical portion fitted to an inner peripheral surface of said outer race,
an annular portion connecting the first hollow cylindrical portion to second hollow cylindrical portion, and
axial grooves which extend through to opposite ends of the first hollow cylindrical portion and are formed at a plurality of circumferential positions at least in an inner peripheral of the first hollow cylindrical portion of each of the end bearings, each of the axial grooves having a circular-arc-shaped cross section in which its radial depth becomes larger toward a central portion of the axial groove.
(7) The one-way clutch according to (6), wherein a circumferential groove having a predetermined axial width and a bottom surface which includes portions of the axial grooves where the radial depth becomes maximum is formed in the inner peripheral surface of the first hollow cylindrical portion of each of the end bearings.